Vibration

A manual task can be defined as any activity requiring a person to use any part of their musculoskeletal system in performing their work. Manual tasks can therefore include:

• Lifting, lowering, pushing, pulling, carrying or otherwise moving, holding or restraining and person, animal or item.
• Repetitive actions
• Sustained work postures and
• Exposure to vibration

Vibration is the rapid motion to and fro of an object such as a pneumatic drill, chainsaw, tractor seating or factory floor. If you could watch a vibrating object in slow motion, you can see movements in different directions. How far and how fast the object moves helps determine its vibrational characteristics. The effects of vibration on the human body can be split into two categories: Whole Body Vibration (WBV) and Hand-Arm Vibration (HAV). The three main contributory factors to both are:

• Length of exposure time;
• Frequency – the rate at which the surface or tool vibrates (measured in Hz)
• Amplitude the size of the vibration

Whole Body Vibration
Whole body vibration occurs when a worker is shaken up and down (vertically), side to side (transversely), or back and forth (linearly).It can be caused by poorly designed or improperly maintained vehicles, platform or machinery resulting in:

• Sprains and strains of joint and adjacent muscles
• Lower back pain (damage to vertebrae and disc as ligaments are loosened from the shaking)
• Motion sickness
• Varicose veins/heart conditions (variations in blood pressure from vibration)
• Stomach and digestive conditions
• Damage to female reproductive organs
• Vision and/or balance disturbances

Controlling Whole Body Vibration Hazards
Reducing whole body vibration in the workplace –

• Eliminate the hazard at the design stage
• Consider changes to a vehicle such as increased seat suspension
• Minimise time spent on a vehicle or platform through job rotation
• Educate employers on the correct use of the equipment
• Ensure there is regular maintenance of all machinery and tool
• Installation of engineering controls on vibrating machinery e.g. mounting machine on a heavy base, installing mountings or sinking the machine into a pit
• Suspension seating
• Seats that can be adjusted from left to right
• Adjustable seat arm rests and back supports
• Spring mounted suspension including shock-absorbers
• Sufficient cab space especially head and leg room
• Seats that can be adjusted according to weight.
• Heavy earth-moving equipment
• Isolated cabs from the frame of the machine
• Pilot-operated controls
• Power steering
• Suspension systems or cushion hitch
• Suspension seats
• Appropriate tyres and tyre pressure

Hand-Arm Vibration
Hand-Arm vibration (also know as white finger or dead finger) occurs in hands and arms when using tools such as chainsaws, chipping hammers or pneumatic drills. The first signs of white finger are tingling or numbness after work. As exposure increases, fingertips nearest the vibration source turn white and stay white for an hour or more. A pins and needles pain develops as circulation returns. After prolonged exposure, the whiteness can spread to the whole hand and fingers may become permanently damaged or gangrenous and require amputation.

Warning signs to look out for from hand-arm vibration include:

• Persistent tingling or numbness
• Loss of strength and coordination
• Loss of sensation

Long term exposure to using hand held tools (e.g. concrete breakers), chainsaws, grinders etc, causes a range of diseases including:

• White finger (dead finger)
• Carpel Tunnel Syndrome
• Sensory Nerve damage
• Muscle and joint damage in the hands and arms
• Loss of strength
• Thoracic outlet syndrome

Controlling Hand-Arm Vibration Hazards
Reducing hand-arm vibration in the workplace –

• Substitute by using non pneumatic low vibration tools where possible
• Always use the right tools – to do the job more efficiently and expose yourself to less vibration
• Check tools before using them to ensure they have been properly maintained to avoid increased vibration cause by faults
• Ensure cutting tools are kept sharp so that they remain efficient
• Reduce the amount of time you use a tool in one go, by doing other jobs in between.
• Educate employers on the correct use of the equipment
• Personal Protective Equipment should include warm clothes to prevent cold and damp situations increasing the risk.

Pneumatic tools Differential pistons to alleviate arm pressure on tool operators Recoil dampening and air cushioning to soften vibration Padded handles to reduce transmission

Chainsaws Anti-vibration chainsaws Fitted spring grips Rubber shock absorbers Rubber shock abs

 

Table taken from the Canadian Centre for Occupational Health & Safety website

Methods of decreasing or eliminating vibration damage may include:

• automation,
• remote control,
• reducing the transmitted vibration,
• use of personal protective equipment,
• proper machinery and plant maintenance,
• lowering the strength of the vibrating source,
• work rest schedules for the operators,
• regular medical checks for workers.

The Approved Code of Practice on Vibration incorporates the following Australian Standards:

Standard	Title	Description
AS 2670	Evaluation of Human Exposure to Whole Body Vibration	Defines methods for the measurement of periodic, random and transient whole-body vibration and indicates the principle factors that combine to determine the degree to which vibration exposure will be acceptable.
AS 2763	Guidelines for Measurement and Assessment of Human Exposure	Sets out general methods for measuring and reporting hand-transmitted vibration exposure and provides guidance for the evaluation of hand-transmitted vibration.

These standards do not define the limits of safe exposure. They present graphics associating different quantities of vibrating energy (ranges) and the human response and possible health effects. These graphics and derived from practical experience and laboratory experimentation. Employers should choose an appropriate range depending on the nature of the work undertaken.

 

USEFUL LINKS

Canadian Centre for Occupational Health and Safety 
What are the ergonomic concerns for selecting powered hand tools?
What are the major ergonomic concerns of a hand tool design?

Calculate the level of vibration you are being exposed to
You can use a vibration calculator to establish what vibration levels you are being exposed to in the workplace from the Health and Safety Executive.

Hand-arm vibration – Advice for employees 
Download the HSE’s free pocket card. This publication contains notes on good practice about hand-arm vibration which you may find helpful.
A handbook on whole-body vibration exposure in mining

Acknowledgements:
http://www.workcover.tas.gov.au
SafeWork SA www.safework.sa.gov.au
Australian Standards 2670 and 2763
Minesafe: Health & Safety: Vibration
Canadian Centre for Occupational Health & Safety website